Wireless power transfer technology was first developed for charging small electric devices, such as toothbrushes and cell phones. Wireless charging systems have now found applications in wireless charging of electric vehicles (EVs). Such EVs include a wireless receiver for receiving a magnetic field from the wireless transmitter and charge a battery of the EV. A key challenge in wirelessly charging EVs is accurate positioning of the EV over the wireless transmitter disposed on the parking spot for efficient charging. Misalignment between the transmitter and receiver can significantly impair the power transfer efficiency. If the magnetic field of transmitter is uniform, misalignment can be tolerated thus making it easy to park the EV over the wireless transmitter.
State of the art wireless transmitters however do not produce a constant magnetic field. The magnetic field intensity of most wireless transmitters is not constant. The uniformity of the magnetic field depends on the size of the receiver coil. Coils that are too small do not provide efficient charging. Furthermore, state of the art wireless transmitters are not designed for the scale of electrical vehicle charging, and either have a small coil size or with distance of only a few millimeters between the transmitter and receiver.